1. Field of Invention
The invention relates to a transmission for a vehicle, and more particularly to a transmission for a vehicle in which a manual transmission is a main transmission.
2. Description of Related Art
To eliminate a clutch operation when a vehicle is started or shifted so as to make a driving operation easy, for a transmission mounted on a vehicle, an automatic transmission is mainly employed using a fluid transmission apparatus, such as a stepped transmission including a planetary gear having multiple speeds or multiple elements, or a stepless transmission such as a continuously variable transmission (CVT) as a starting apparatus. Further, the stepped transmission tends to have multiple speeds in order to respond to a requirement of securing drivability and improving a specific fuel consumption which is indispensable for energy saving.
Meanwhile, an automatic transmission using the fluid transmission apparatus as mentioned above has a disadvantage in terms of fuel consumption in comparison with a conventional manual transmission using a dry type single disc clutch because a transmission efficiency of the fluid transmission apparatus is particularly low, though an improvement is made, for example, when a lock-up clutch is provided for the purpose of improving the low transmission efficiency. On the other hand, in the case of a conventional manual transmission, which is advantageous in terms of the transmission efficiency, since it is necessary to pass through a neutral state in which power transmission is interrupted at a time of shifting, irrespective of whether the clutch operation is manually performed or automatically performed, Applicants note that, smoothness in acceleration tends to be insufficient.
Further, with regard to multiple speeds, in the case of the automatic transmission mentioned above, a planetary gear is necessarily made to have multiple speeds or multiple elements, or the number of friction elements or engagement elements such as clutches, brakes, one-way clutches and the like, for controlling the planetary gear, is increased. Accordingly, in a transmission for a vehicle in which a mounting space is severely limited, it is hard to take an essential measure for the space, though it is possible to improve a layout of the friction elements or the engagement elements with respect to the planetary gear. On the other hand, in the case of a manual transmission, since an increase of the number of the shift speeds directly causes an increase of gear pairs, the transmission needs to be large, and in particular, the axial length needs to be increased. Meanwhile, in the case of the manual transmission, a main transmission and a sub transmission can be combined, and multiple speeds can be provided while suppressing the increase of the gear pairs by the relevant control. However, in this case, both of the main and sub transmissions need to perform shifting simultaneously, so that a significantly complex and hard control is required. As mentioned above, each of the automatic transmission and the manual transmission has advantages and disadvantages, and it is hard to provide an overall solution for the problems using conventional techniques.